Three cascade solar cells with graded band-gap layer on the base of GaAs–AlGaAs heterosystem

A new structure of three cascade solar cells with graded band-gap layer on the base of GaAs–AlGaAs heterosystem is designed to decrease the thermal losses, arising as a result of absorption of short-wavelength radiation. These solar cells were created by combining liquid-phase epitaxy with gas-phase zinc diffusion technologies. In these structures multilayer cascade elements reduce losses, caused by generation of “hot” carriers and the upper graded band-gap layer improves the conversion of short-wavelength radiation. The cell structure exhibited high short-wavelength sensitivity and the following parameters (under 1-sun conditions): open-circuit voltage (V_oc=1.03 V); short-circuit current (I_sc=24.9 mA/cm²); fill factor (FF=0.74) and efficiency (η=22.3%). Therefore it can be successfully utilized as power supplies in high-located areas, and as sensors of ultra-violet radiation.